Ganpat went to fruit market with a certain amount of money. With this money he can buy either 50 oranges or 40 mangoes. He retains 10\% of the money for taxi fare. If he buys 20 mangoes, the number of oranges he can buy is
(a)6
(b)18
(c)20
(d)25
Answer
Answer (as printed): C
Explanation
Suppose Ganpat has ₹ $x$. Then, cost of 1 orange $=₹\left(\frac{x}{50}\right)$; cost of 1 mango $$=₹\left(\frac{x}{40}\right) .$$ Money left after paying taxi fare $=90 \%$ of $₹ x=₹ \frac{9 x}{10}$. Money spent in buying 20 mangoes $=₹\left(\frac{x}{40} \times 20\right)=₹ \frac{x}{2}$. $$\text { Money left }=₹\left(\frac{9 x}{10}-\frac{x}{2}\right)=₹ \frac{4 x}{10}=₹ \frac{2 x}{5} .$$ ∴ Number of oranges that can be bought $$=\left(\frac{2 x}{5} \times \frac{50}{x}\right)=20 .$$
Explanation as extracted from the printed page; notation may be imperfect.